The conservation value of rocky shores

Pragmatic nature management policies should be based on an awareness of the sometimes conflicting demands of development and conservation and the limited resources available to meet conservation aims. The resolution of such conflicts of interest and the allocation of resources should be based on an objective assessment of the ‘conservation value’ of natural features. Criteria for assessing ‘conservation value’ remain the subject of debate.

In this section, we discuss whether rocky shore communities fulfil each of Hiscock’s (draft, 1998) criteria and some additional criteria which we believe are important.

Hiscock (1998b) states that a habitat, community or species is likely to be considered ‘important’ in terms of conservation if it is

Rare or restricted in its distribution

Rocky shore habitats are common on the shores of Northwestern Europe and especially the UK. The majority of species belonging to rocky shore communities have extensive geographical ranges. The location of any population within this range will be influenced by latitude, salinity, wave exposure, hydrodynamic factors on a variety of scales and the presence of other species. However, most rocky shore species are found at numerous sites. Rocky shores and their species are neither rare nor restricted in their distribution. However, some types of rocky shores, for example those with a limestone or siltstone substratum are represented by few examples in the UK. The widespread distribution of rocky shores inevitably means that they form part of other habitats such as saline lagoons which are restricted in their distribution. Conservation efforts for such habitats should be at a scale which encompasses a cross section of the component subhabitats. Rocky shores in such areas should therefore be considered part of a rare habitat.

In decline or has it been

Rocky shore communities in heavily industrialised areas such as the Mersey estuary have been severely affected by anthropogenic impacts. These shores no longer support many of the flora and fauna associated with a healthy rocky shore community. There has been no significant recent increase in the loss of rocky shore habitats. The historical loss of rocky shore communities due to anthropogenic impacts is devastating in terms of the local ecology but has little apparent effect on communities of the rest of the UK’s numerous rocky shores. However, pollution has caused the decline of some rocky shore species, most notably the dogwhelk (Section IV.B.2). Although the dogwhelk population has suffered local extinction, dogwhelks remain a common species throughout the UK. Acute impacts such as the Torrey Canyon oil spill have devastated rocky shore communities on long stretches of coastline. These communities have a demonstrable capacity for recovery due largely to the supply of larvae and propagules from more distant populations. The whole U.K. rocky shore habitat is not and has not been in significant decline.

A high proportion of the regional or world population or extent

The UK coastline comprises a significant proportion of Europe’s rocky shores. Shores in the Baltic have suffered considerable anthropogenic impact. Those in the North Sea lack the high diversity of species seen on Atlantic coasts. The UK is also the meeting point between the distributions of many Northern and Southern species. Therefore, the rocky shores of the UK and especially those on the West coast are very significant from this point of view. Rocky shores within individual SACs do not represent a high proportion of the regional extent.

A keystone species providing a habitat for other species

Many of the dominant species on rocky shores do provide habitat for other species. Significant examples include mussel beds (Seed, 1996), algal canopies, beds of red algae and Sabellaria reefs (the subject of another SAC review). Many species in rocky shore communities, especially grazers, predators and major space occupiers also have a significant effect on other species through their biological interactions. Therefore, many of the dominant species on rocky shores fulfil this criterion.

A biotope with a particularly high species richness

Since rocky shore biotopes rarely exist independently of other units of the community and may not be stable in time, conservation of individual biotopes does not appear to be a workable strategy. The rocky shore community consists of a number of zoned species assemblages arranged along a fairly narrow strip. The diversity of species within this is influenced by each of the major gradients which affect the habitat; wave action, emersion, latitude and salinity. Species richness may not be the most appropriate measure of biodiversity on rocky shores since many bedrock shores are dominated by large numbers of a few species. However, rocky shores, especially those rich in microhabitats, include a diverse array of species in a limited area.

Particularly good or extensive representatives of their type

The general comments on UK rocky shores made above apply equally to this criterion. UK rocky shores are both extensive and important. Intertidal reefs are noted as a major feature in four out of 12 demonstration SACs and eleven out of 56 potential SACs (Firth of Lorn, Flamborough Head, Lochs Duich, Long and Alsh, Papa Stour, Pembrokeshire Islands, Lleyn Peninsula and the Sarnau, South Wight Maritime, St Kilda, Thanet Coast and The Lizard). Lochs Duich, Long and Alsh include particularly good examples of sheltered rocky shores. The Pembrokeshire Islands include good examples of exposed rocky shores. Papa Stour and St Kilda also include very exposed shores with a strong oceanic influence, while the Berwickshire coast has good examples of North Sea shores. The rocky shore communities of the Firth of Lorn, the Thanet Coast and the Isle of Wight are of relatively low biodiversity while those of the Lleyn Penninsula have a high diversity. Thus, the rocky shores of some Candidate and Qualifying SACs fulfil this criteria while others do not. The UK coast includes plenty of examples of biologically diverse rocky shores which are not contained within potential SACs.

A habitat or community could also be considered to be ‘important’ if it is:

Of significant economic value

Rocky shore species, especially winkles, edible crabs and seaweeds (fucoids and kelp) are all harvested commercially from UK rocky shores. Rocky shores also provide important habitat for corkwing wrasse which are used in the aquaculture industry. Management policies for SACs should prevent practices, including harvesting, which are likely to result in significant impacts to species or communities. Immigration from protected areas can replenish stocks of animal species in areas where they are exploited and natural recovery of seaweed crops occurs where these have been harvested carefully (Ascophyllum spp. and Laminaria hyperborea). Since the rocky shores which would be encompassed within SACs represent only a small fraction of this habitat in the UK, it is unlikely that they would play a major role in preserving stocks of commercially important species.

Of aesthetic, symbolic or recreation value

The only benthic habitats which many people will see first hand are those in the littoral zone, which consequently have a higher aesthetic value. Sandy beaches are popular with the public as traditional recreational areas. Although rocky shores are less popular, they can be used by high numbers of visitors (Fletcher, 1997). The value of rocky shores as a teaching aid is demonstrated by the many field trips run by schools, colleges and universities. We feel that the success of conservation projects relies heavily on public involvement and goodwill. Rocky shores are a natural feature of some potential SACs that can be used to promote public awareness of marine ecosystems and generate support for the conservation objectives of the site.

Ecologically important to other species or communities

Rocky shores are net exporters of energy to both marine and terrestrial ecosystems. They provide food to shore and sea birds, otters and marine fauna. They also represent an important seasonal food resource for migrating shorebirds such as the purple sandpipers, Calidris maritima. However, there are no known examples of species living in other habitats that rely exclusively on rocky shores for food.

Littoral habitats are unique amongst all marine habitats in their degree of accessibility. Both the public and those involved in study or management of the shore can get direct access without the need for specialist equipment or training. The majority of species associated with sediment beaches are infaunal and must be sampled using time consuming, destructive methods. In contrast, the dominant species on rocky shores are exposed and visible at low tide. The condition of the community can be rapidly assessed using non-destructive methods. Rocky shore communities are well studied and understood. They can therefore be monitored easily and meaningful conclusions can be drawn from the results of this monitoring. Impacts on rocky shore communities may be indicative of wider impacts affecting the marine community. Therefore, the main conservation value of rocky shores lies in the accessibility of their biological communities and the benefits of this to monitoring programmes and public involvement.

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